mirror of https://github.com/thesofproject/sof.git
98 lines
3.3 KiB
Matlab
98 lines
3.3 KiB
Matlab
function cnv = src_param(fs1, fs2, coef_bits, q, gain)
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% src_param - get converter parameters
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%
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% cnv = src_param(fs1, fs2, coef_bits, q, gain)
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%
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% fs1 - input rate
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% fs2 - output rate
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% coef_bits - word length identifier
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% q - quality scale filter bandwidth and stopband attenuation,
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% 1 is default
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% gain - overall gain of SRC, defaults to -1 (dB) if omitted
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%
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% Copyright (c) 2016, Intel Corporation
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% All rights reserved.
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%
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% Redistribution and use in source and binary forms, with or without
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% modification, are permitted provided that the following conditions are met:
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% * Redistributions of source code must retain the above copyright
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% notice, this list of conditions and the following disclaimer.
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% * Redistributions in binary form must reproduce the above copyright
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% notice, this list of conditions and the following disclaimer in the
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% documentation and/or other materials provided with the distribution.
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% * Neither the name of the Intel Corporation nor the
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% names of its contributors may be used to endorse or promote products
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% derived from this software without specific prior written permission.
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%
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% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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% AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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% IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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% ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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% LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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% CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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% SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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% INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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% CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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% ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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% POSSIBILITY OF SUCH DAMAGE.
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%
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% Author: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>
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%
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% Note: firpm design with rs 93 dB, or kaiser with 69 dB rs is fair quality.
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% Both give about -80 dB THD+N with 24 bit coefficients. With 16 bit
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% coefficients THD+N is limited to about -76 dB.
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if nargin < 5
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gain = -1;
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end
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if nargin < 4
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q = 1.0;
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end
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%% Create plots
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cnv.do_plots = 0;
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%% Copy input parameters
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cnv.fs1 = fs1;
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cnv.fs2 = fs2;
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cnv.coef_bits = coef_bits;
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%% FIR design
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cnv.design = 'kaiser'; % Use firpm or kaiser
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%% Default SRC quality
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cnv.c_pb = q * 20/44.1; % Gives 20 kHz BW @ 44.1 kHz
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cnv.c_sb = 0.5; % Start stopband at Fs/2
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cnv.rs = 63; % Stopband attenuation in dB, initial value that will stepped to meet THD+N
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cnv.rs_max = 120; % Do not exceed this
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cnv.rp = 0.1; % Passband ripple in dB
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cnv.rp_tot = 0.1; % Max +/- passband ripple allowed, used in test script only
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cnv.gain = gain; % Gain in decibels at 0 Hz
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%% Constrain sub-filter lengths. Make subfilters lengths multiple of four
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% is a good assumption for processors.
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cnv.filter_length_mult = 4;
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%% Exceptions for quality
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if min(fs1, fs2) > 80e3
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cnv.c_pb = 24e3/min(fs1, fs2); % 24 kHz BW for > 80 kHz
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end
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%% Sanity checks
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if cnv.c_pb > 0.49
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error('Too wide passband');
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end
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if cnv.c_pb < 0.10
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error('Too narrow passband');
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end
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if cnv.rs > 160
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error('Too large stopband attenuation');
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end
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if cnv.rs < 40
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error('Too low stopband attenuation');
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end
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